Containers of aluminum and aluminum alloys are manufactured by a drawing and forming operation, commonly referred to as drawing and ironing. This operation results in the deposition of lubricants and forming oils on the surfaces of the containers. In addition, residual aluminum fines are deposited on the surfaces, with relatively larger quantities present on the inside surface of the container.
Prior to processing the containers, e.g. conversion coating and sanitary lacquer deposition, the surfaces of the containers must be clean and free of water breaks, so that no contaminants remain on the surfaces which will interfere with further processing of the containers.
Compositions currently used commercially for cleaning such aluminum containers are aqueous sulfuric acid solutions containing hydrofluoric acid and one or more surfactants. Such cleaning solutions are quite effective and have many advantages. However, there are also some disadvantages associated with such cleaning compositions. For example, fluoride containing compositions are capable of dissolving stainless steel and other iron alloy equipment commonly utilized in the container cleaning lines. Also, hydrofluoric acid and fluorides present in spent cleaning baths and rinse water present an environmental problem in their disposition.
Compositions and methods for the low temperature cleaning of aluminum surfaces are disclosed in U.S. Pat. No. 4,009,115 issued Feb. 22, 1977 to Robert Eric Binns, U.S. Pat. No. 4,116,853 issued Sept. 26, 1978 to Robert Eric Binns, U.S. Pat. No. 4,124,407 issued Nov. 7, 1978 to Robert Eric Binns, and U.S. Pat. No. 3,969,135 issued July 13, 1976 to Peter F. King, et al. These patents disclose cleaning compositions containing sulfuric acid, hydrofluoric acid or a fluoride salt, and a surfactant.
Compositions and methods for the high temperature cleaning of aluminum surfaces are disclosed in many patents, a typical example of which is U.S. Pat. No. 3,635,826 issued Jan. 18, 1972 to Andrew J. Hamilton. Such high temperature compositions and processes are now seldom used due to escalating costs of energy.